1. Field of the Invention
The present invention relates to an optical apparatus, and more particularly to an optical apparatus that has a recording mode that is switchable between motion picture recording and still picture recording.
2. Description of the Related Art
A camera that can provide both motion picture photography and still picture photography, such as a digital video camera that has a function of taking a still picture and a digital still camera that has a function of taking a motion picture. In general, voices are simultaneously recorded in the motion picture photography. At that time, it is necessary to prevent recording operational noises from a motor that is driving an optical element, such as a focus lens and a zoom lens. In addition, in the still picture photography, it is necessary to drive the optical element and to instantly prepare for a photography action so as not to miss the photography timing.
Japanese Patent Laid-Open No. 2004-004362 discloses a digital camera that can provide both the motion picture photography and the still picture photography. This digital camera drives a stepping motor that moves a lens, by using a two-phase excitation driving method in the still picture photography. In the motion picture photography, the stepping motor is driven by a micro step driving method that promotes silent driving of the stepping motor, and reduces operational noises of the motor to be recorded in the motion picture photography.
Japanese Patent Laid-Open No. 09-331666 is another prior art.
However, the stepping motor when driven at a high velocity cannot maintain synchronization between a driving pulse and rotor's rotations and is likely to step out. In an attempt of high-velocity driving using the stepping motor, it is conceivable to use a motor with a large step width or to lower a reduction ratio of a transmission mechanism. However, this scheme degrades a driving resolution of a lens, and it is difficult to drive the lens with high precision. In addition, in an attempt to obtain a high resolution necessary to drive a lens using the stepping motor, it is conceivable to use a motor with a small step width or to increase a reduction ratio of the transmission mechanism. However, this scheme lowers the driving velocity of the lens, and it is difficult to instantly prepare for a photography action.